Electric heated sucker rod

ABSTRACT

A vertical sucker rod string formed of lengths of sucker rods, each having means for attachment at each end thereof to adjacent sucker rods, is provided with electric heating means for maintaining the temperature of the crude oil being pumped to the surface above a preselected level to prevent the congealation of paraffin. An electric heating element coextensive in length with the rod is disposed in a small diamater bore hole in each rod. A solid heat conducting electrical insulation completely fills the bore hole in the rod around the heating element. Couplings are provided between adjacent sucker rods to obtain electrical continuity between the heating element in each of the adjacent rods. A terminal coupling provides a connection between the heating element of the lowermost sucker rod and the sucker rod, whereby the sucker rod string serves as a conductor to complete the circuit for energizing the heating elements.

United States Patent 1191 Palone Jan. 7, 1975 41 ELECTRIC HEATED SUCKERROD 57] ABSTRACT Inventor: Richard 1332 Efie, A vertical suckerrod'string formed of lengths of Tl11$a,01 1a- 74112 sucker rods, eachhaving means for attachment at [22] Filed, June 12 1973 each end thereofto adjacent sucker rods, is provided with electric heating means formaintaining the tem [21] Appl. No. 3 9, perature of the crude oil beingpumped to the surface above a preselected level to prevent thecongealation of paraffin. An electric heating element coextensive in[52] US. Cl 219/278, 166/60, 2211996550461, length with the rod isdisposed in a Small (Hammer [51] Im Cl H05) 3/02 E2") 43/24 bore hole ineach rod. A solid heat conducting electri- 58 Field of Search 219/277,278, 541, 307, g f fills the we y 219/306; 56/57, 58 6042302, 303 aroundt e eatmg e ement. Coup 1ngs are prov1 e 7 between ad acent sucker rodsto obtaln electncal con- [561 1:12:21 $511 2"5351115131'Zi$"$$i ci fniiition between the heating element of the lowermost I gg t y sucker rodand the sucker rod, whereby the sucker rod string serves as a conductorto complete the cir- 1,970,295 8/1934 F1tzpatr1ck r 219/278 UX cuit forenergizing the heating elements 2,598,280 5/1952 McLean 219/278 X2,728,396 12/1955 Carpenter. 219/277 X 2,812,818 11/1957 Brusco 219/278x 4 Chums 4 Drawmg F'gures Primary Examiner-A. Baltis a Attorney, Agent,or Firm-Head & Johnson 46 42 40A 52 40B 40 44 42 3e 1" l 1 i If 4 1. 1

l T :Iklffjjll': If: llilllji'lkl' I I I II i L 36 3 4, 51) 42 46 36 lNm I //l 36 44 38 36 ELECTRICAL RESISTANCE 3 HEATING ELEMENT ELECTRICHEATED SUCKERZ non BACKGROUND AND OBJECTS'bF-J "IE INVENTION When anoiliwell is completed the pressure of the oil producingformation'sometimes is' sufficiently.great-ta cause the crude oil to beforced to the earths surface. Such wells are called flowing wells.Eventually, however, inmost instances the pressure of the formationfalls below that which is necessary to force the,crude 'oil to the earths surface. This requires some means of pumping the crude oil. The mostcommonly" used means of lifting crude oil from a subterraneanformaperature. At the temperat aie in the oil producing forrnation thecrude oil is in Iiquid form but as it is pumped to the earths surfa ceina tubing string it passes upwardly through areasa of gradually decliningtemperatures. If Cl'UdQ/bI lfihaS a high paraffin content which congealsat higher than normal temperatures, an area .is reached iii-the upwardtravel of the crude oil wherein the temperature inside the tubing fallsbelow that at which t'he paraffin contentof the crude congeals. At

pletely pluggedby the congealed paraffin.

In some areas the problem of congealed paraffin is such that wellscannot be economically produced. Othv ers have suggested means ofcombating the problem of paraffin formation in wells, such as theme ofscrapers attached to the exterior of the sucker rods which areconfigured to scrape the interior of the tubing to dislodge paraffin asit accumulates. The dislodged paraffin 40 is then carried upwardly bythe flow of fluid to the surface. This procedure, however, is notcompletely satisfactory in all instances since in some cases the ratethe. paraffin congeals is so great the scrapers cannot keep itdislodged. In addition, the scrapers do not help prevent theaccumulation of paraffin on the sucker rods and thereby even though theinterior of the tubing is scraped the accumulation of paraffin aroundthe sucker rods can soon approach that at which the interior of thetubing is blocked.

Others have provided heating elements positioned in the bottom of wellsincluding electrical conductors attached to the exterior of the tubing.In some instances the heating elements are attached to the tubing atpoints above the lowest level at which the crude oil reaches thetemperature at which paraffin content begins to congeal. In this methodthe electrical conductors to the heating elements are carried on theexterior of the tubing. This procedure works satisfactorily except thatit is difficult to run tubing with electrical conductors. In addition,any failure of the heater or the conductors requires that the tubingstring be pulled, a relatively expensive process.

This invention is directed towards a simplified means of maintaining thetemperature of crude oil as it is pumped to the earths surfacesufficiently high to prevent the formation of paraffin. The inventionoverthis point the paraffin congeals on the inside of the tub- 30 figand on the outside of the sucker rod. If the process continues longenough the tubing can become comcomes the disadvantages of the otherknown methods of combating paraffin accumulation in oil wells.

It is therefore an object of this invention to provide are improvedmeans of maintaining the temperature Within the interior of the tubingstring utilized to pump crude oil so as to prevent paraffincongealation. More particularly, an object of this invention is toprovide a sucker rod configuration including means of applyingelectrical energy to the sucker rod so as to raise the temperaturethereof and thereby raise the temperature of the crude oil pumped by thesucker rod to the point wherein the temperature of the crude oil willnot fall below that at which severe paraffin congealation takes place.

" Still more particularly, an object of this invention is to provide asucker rod including improved means of heating the sucker rod withelectrical energy.

Another object of this invention is to provide a sucker rod includingmeans of electrically heating the sucker rod and means of conductingelectrical energy from one sucker rod to the next.

Another object of this invention is to provide an arrangement forelectrically heating sucker rods as used in producing oil wells toprevent the accumulation of paraffin within tubing and including meansof conduct ing the heating element to ground at a preselected pointwithin the sucker rod string.

These and other objects will be fulfilled in the following descriptionand claims taken in conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of apumping unit showing means of use of the electric heating sucker rods ofthis invention.

' FIG. 2 is a cross sectional view of a coupling and an electricallyheated sucker rod showing means of electrically coupling one sucker rodto another.

FIG. 3 is a cross sectional view taken along the line 3-3 of FIG. 2.

' FIG. 4 is a cross sectional view as in FIG. 2 showing a terminalarrangement for connecting the electrically heated wire to the suckerrod body.

. SUMMARY The invention is a sucker rod construction providing I meansof heating petroleum produced in an oil well so as to raise thetemperature of the petroleum above that which results at which paraffincongeals. The sucker rod, which has means at each end for attachment toan adjacent sucker rod, has a small diameter axial bore through theentire length. An electrical heating element is positioned within thebore andis surrounded by heat conducting electrical insulation. Means isprovided for applying voltage to the element to cause current to flowthrough it and thereby heat it. Heat flows through the electricalinsulation to the sucker rod and then to the petroleum fluid beingpumped to the surface. I-Ieat is thereby applied to the petroleum fluidto maintain the temperature thereof above the congealing temperature ofparaffin. Couplings are provided between adjacent sucker rods to obtainelectricalcontinuity between the electrical heating element in each ofthe adjacent sucker rods. Terminal coupling is provided for connectingthe lower end of the heating element in the lowermost sucker rod to thesucker rod. In this way the sucker rod string serves as a conductor to'jcompletethecircuit by whichthe heating element is energized. a K

DESCRIPTION PREFERRED EMBOIDIMENT 1 Referring to the drawiiigs and firstto FIG. 1 the basic arrangement for pumping an oil well byreciprocationof a sucker rod stripg is shown. The arrangement int achme nt to apolished rod 18. The polished rod extends through a stuffing box 20 in awell head 22 attached to the upperend of casing ,24.' Pipe 26 extendsfrom 'the well head and'carries the produced petroleum his a tankbattery'for further distribution;

The end'of thewalking beam 12 opposite horse head 16 is attached to acounter weight 28- driven by a crank arm 30, the counter-weight andcrank arm being attached to, a' connecting rod ,32extending to thewalking beam 12. The crank arm 30 isattached to a shaft v34 rotated by agear box (not 'shown),;driven in turn by a prime mover, such as an-electric"moto r., or engine, also not shown. By the rota'tion' of shaft34" the walking upward extension of the string of sucker rods and isdifferent only thatit-has a smooth external configuration jto=reciprocateagainst packing within the stuffing box "/20 whichpreventsproduced crude oil from escaping outwardly of the stuffing boxrather than flowing embodiment illustrated the heating element is intheform of a resistance wire 46. When current flows through wire 46 heat isimparted to the sucker rod 36 and thereby to the crude oil surroundingthe sucker rod so as to maintain the temperature above that at whichparaffin will congeal.

beam-"l2is pivotally reciprocated moving horse head 5; 16 up and downand thereby reciprocating the polished -'rod 18. The pumping jack of FIG1 deseribed to this "point is a standard means of reciprocating suckerrods in an oil well and form no'part of the invention. The polished rod18 connects to a string of suckerodswhich extend within a tubing (notseen) within the: casing24, the sucker rod and tubing extendingdownwardly within the earth to a subterranean crude oil producingformation. In effect, the polishedrod 18'is'an rods as is.;require d.

. To prevent the resistance heating wire 46 from contacting the suckerrod the wire is surrounded by electrical insulation 48 which may be of avariety of compositions and may be, as an example, a mineral insulation.While the main function of the insulation 48 is to prevent electricalcontact between the resistance wire 46 and the sucker rod 36 theinsulation preferably is of a type which is a good heat conductor so asto conduct the heat of the resistance wire to the surrounding suckerrod.

In order to connect the resistancewires 46 of adjacent sucker rodsmaking up a sucker rod string, it is necessary that electricalcontinuity be had from one rodto another. FIG. 2 shows one method ofaccomplishing this. In this arrangement an axial conductive element 50is centrally positioned within coupling in 52 which may be formed of anyinsulati'ng material,

such as plastic. It can be seen that the resistance wires may beinterconnected for FIG. I shows one means ofimparting electrical en-.ergy t o the sucker-rods. By means of a transformer54 current issupplied' to conductors 56A and 56B. Con- 'duc tor 56A is attached tothe exterior of the polished rod ISQandtherebyJtO the sucker rod string.Conductor 56.1355 attached to'g'the' resistance wire 46 which extendsthe resistance-wire in' each 'ofthe succeeding lower "lengths'of'suckerrods36.

Onejmethod of.;providingjalreturn current'flow isshown in FIGS. land 4.Conductor 56A-is connected i nternally. of the1polished rod 18 and isconnected to to the exterior ofpolished rod 18 and thereby to each therods areiofsolid configuration. ,However,,'in the present invention thesuckerrodsineludefanaxial bore hole 38 through-the entire} length ofeach rod; 'Ass'h'own in FIGS. 2 and 4 onlyafs nall portion of thelengths of i the sucker rods areshownln FIG. 2 the righthand-portion'shows an end of a sucker rodin' cross "section-while Iin-the left hand portion an end of a suekerrodisshow'n" in exteriorconfiguration, with a coupling .40 shown in" I cross sectionalconfiguration as used to connect in'end to'end relationship the adjacentsucker rods. Each of f the suckerrods 36 includesan enlarged shoulderpor'-' tion 42which. terminates inan externally threaded pin of thesuccessive lengths of 'suckerf rods '36. To provide a return path ofcurrent flow the resistance wire 46 must be connected at some point tothe sucker rod string. In order: to achieve this arrangement FIG. ,4

shows a terminal conductive means including a terminal conductiveelement 58 positioned in the interiorlof a coupling 40. The conductiveelement 58 isjof cohiduc-iv f I tive materiahsuch as copper or copper'a'll oyl or the lik ef vand communicates the end 46A of there'sistancewire portion 44. The interior of the couplings 40 is threaded at 40A and408 to threadably receive the externally sucker rods 36 is an electricalheating element. In the portions 58A and 588 at opposite ends thereof;Protr sion portion 58A contacts the end 46A of resistance wire 46. andprotrusion 58B engages the pin portion 44 of the'next lower sucker rod36 to insure connection the resistance wire 46'tfo the sucker rods 36.In addition 'to contacting the 'pin portion 44 the next lower adja':cent sucker rod 36 the conductive element 58 also providescul'rutflow-through coupling 40. Thus,'as showirijf in FIG. 1 the "conducto'r56B communicates with the re- 156 to the couplings 40 and thereby back to suck er rods 'i v '36. f

The conductive element 58 includes axialprot'riisi sistance element 46i'na sucker rod string and conductor 56A connects to the-sucker rodstringitself through i polishedrod 18. so thatacomplet'e path of currentflow is provided.

as many successive sucker As crude oil is pumped upwardly in a tubingthe temperature gradually lowers until a point is reached wherein withhigh paraffin content crude, congealing begins. By the use of thisinvention the number of sucker rods 36 which must be heated can beregulated so as to extend downwardly into the well only that distancerequired to provide heat to the crude oil in the upper portion of thetubing string. In some wells the length of the sucker rod string whichmust be heated will be substantially the full length of the tubing. Inother wells only the upper portion of the column of fluid being producedneed by heated. Between each adjacent length of sucker rod 36 whereinthe lower rod is to be heated the conductive element 50 as shown in FIG.2 is utilized. At the lower end of the string of sucker rods requiringheating a terminal conductive element 58 as shown in FIG. 4 is utilized.The sucker rods below element 58 are not heated.

While the invention has been described with a certain degree ofparticularity it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the embodiments set forth hereinfor purposes of illustration, but is limited only by the scope of theattached claim or claims, including the full range of equivalency towhich each element thereof is entitled.

What is claimed:

1. In an oil well including a vertical string of sucker rods extendingfrom the earths surface downward to a subterranean pump including meansat the surface for reciprocation of the sucker rods for actuation of thepump, a means for maintaining the temperature of the crude oil beingpumped to the surface above a preselected level to prevent thecongealation of paraffin, comprising:

a vertical sucker rod string formed of lengths of sucker rods, eachsucker rod having means for the attachment at each end thereof toadjacent sucker rods, each sucker rod having an axial small diameterbore hole therein;

an electrical heating element positioned in said bore hole;

solid heat conducting electrical insulation completely filling said borehole in said sucker rod surrounding said heating element, and

means of applying a voltage to cause current to flow through saidheating element.

2. A means for preventing congealed paraffin formation in an oil wellaccording to claim 1 wherein said means of applying voltage to saidresistance wire includes two conductors having voltage thereacross, oneof the conductors being electrically attached to said heating elementand the other electrically attached to said sucker rod and wherein thelower end of said heating element is electrically connected to saidsucker rod.

3. A means for preventing congealed paraffin formation in an oil wellaccording to claim 2 including couplings between adjacent sucker rods insaid string of sucker rods, each said coupling providing electricalcontinuity between said sucker rods, each said coupling being tubularand having a central insulating element therein positioned between theends of adjacent sucker rods, and an axial conductive element supportedby said insulating element, said conductive element providing electricalcontact between said heating element positioned within adjacent suckerrods.

4. A means for preventing congealed paraffin formation according toclaim 2 including a terminal coupling means between adjacent sucker rodspositioned in said sucker rod string at the lowermost point wherein heatis required to maintain the crude oil above the preselected temperaturelevel, the terminal coupling being tubular and threadably receiving atthe upper end a sucker rod having said heating element therein andthreadably receiving at the lower end a lower sucker rod and saidcoupling having a conductive element therein contacting said heatingelement and providing continuity between said heating element and saidlower sucker rod.

1. In an oil well including a vertical string of sucker rods extendingfrom the earth''s surface downward to a subterranean pump includingmeans at the surface for reciprocation of the sucker rods for actuationof the pump, a means for maintaining the temperature of the crude oilbeing pumped to the surface above a preselected level to prevent thecongealation of paraffin, comprising: a vertical sucker rod stringformed of lengths of sucker rods, each sucker rod having means for theattachment at each end thereof to adjacent sucker rods, each sucker rodhaving an axial small diameter bore hole therein; an electrical heatingelement positioned in said bore hole; solid heat conducting electricalinsulation completely filling said bore hole in said sucker rodsurrounding said heating element, and means of applying a voltage tocause current to flow through said heating element.
 2. A means forpreventing congealed paraffin formation in an oil well according toclaim 1 wherein said means of applying voltage to said resistance wireincludes two conductors having voltage thereacross, one of theconductors being electrically attached to said heating element and theother electrically attached to said sucker rod and wherein the lower endof said heating element is electrically connected to said sucker rod. 3.A means for preventing congealed paraffin formation in an oil wellaccording to claim 2 including couplings between adjacent sucker rods insaid string of sucker rods, each said coupling providing electricalcontinuity between said sucker rods, each said coupling being tubularand having a central insulating element therein positioned between theends of adjacent sucker rods, and an axial conductive element supportedby said insulating element, said conductive element providing electricalcontact between said heating element positioned within adjacent suckerrods.
 4. A means for preventing congealed paraffin formation accordingto claim 2 including a terminal coupling means between adjacent suckerrods positioned in said sucker rod string at the lowermost point whereinheat is required to maintain the crude oil above the preselectedtemperature level, the terminal coupling being tubular and threadablyreceiving at the upper end a sucker rod having said heating elementtherein and threadably receiving at the lower end a lower sucker rod andsaid coupling having a conductive element therein contacting saidheating element and providing continuity between said heating elementand said lower sucker rod.